Recently, it is designed to attain miniaturization and density growth of electronic equipment, by integrating a passive part, such as a capacitor or inductor, conventionally mounted on a ceramic substrate surface, within a ceramic multilayer substrate. Such a ceramic multilayer substrate is produced by forming a green sheet from a slurry of a dielectric porcelain composition and an organic solvent by doctor blade method followed by drying, printing a wiring conductor on the top surface of the sheet, forming a laminated body by laminating such green sheets of the same dielectric porcelain composition as described above, and co-firing it.
Such a ceramic multi-layer substrate uses Ag or Cu with small specific resistance as the wiring conductor for performing high-performance signal processing at a high speed. Therefore, various ceramic materials have been developed for co-firing with Ag and Cu at temperatures lower than 962° C., the melting point of Ag, and 1084° C., the melting point of Cu.
For example, a ferrite of Fe2O3, ZnO, CuO and NiO system is described in Japanese Patent Publication Nos. 2001-10820A and 2003-272912A.
In composite electronic parts having magnetic and dielectric materials and Ag conductors, the dielectric material parts of the most of them has a relative permittivity of 100 or lower. Further, in composite electronic parts of magnetic and dielectric materials having a dielectric material part of a relative permittivity of 100 or more, the dielectric constant is of a level slightly exceeding 100 in the case that the main components of the dielectric material do not include Pb (Japanese patent publication No. 2003-37022A and WO 2006/085625).
Further, the applicant discloses, in Japanese Patent Publication No. 2007-290940A, a dielectric composition having a high dielectric constant without containing lead, which can be fired at a low temperature by adding specific amounts of CaO and Bi2O3 to barium titanate.
Further, in coil parts, such as a laminated inductor, using a ferrite material as its core, the inductance is lowered as a direct current voltage is applied. Therefore, in electronic parts using superimposed direct current, the reduction of the inductance is a major factor deciding the rated current. It is thus demanded a material having an excellent DC superposition characteristics as the ferrite material used for the core of the coil part, for improving the rated current.
For example, according to Japanese Patent Publication No. 2006-151742A, bismuth oxide and titanium oxide are added to an NiCuZn series ferrite material for improving the DC superposition characteristics.
Further, the applicant discloses, in Japanese Patent Application No. 2009-82211 (Japanese Patent Publication No. 2010-235328A) that specific amounts of bismuth oxide, titanium oxide and barium oxide are added to an NiCuZn series ferrite material for improving the DC superposition characteristics.
In ferrite and LTCC products using Ag conductors, it is possible to attend new needs by combining passive parts having high capacitances. For example, it is necessary a composite electronic part of magnetic and dielectric materials having a higher capacitance for miniaturizing, and reducing the required space of, parts for shielding low frequency noise generated in electric source systems. That is, it is necessary to laminate and integrate a ferrite layer forming a coil or inductor and a high dielectric constant ceramic layer forming a condenser or capacitor. Further, it is necessary that the high dielectric constant ceramic layer and ferrite layer can be densely sintered at a low temperature region of 1000° C. or lower and can be joined with each other without delamination and cracks.
Moreover, between the high dielectric constant ceramic and ferrite layers, the components are diffused to each other during the co-firing, so that the dielectric property tends to be deteriorated. It has not been known a composite electronic part solving these problems.
Besides, the applicant discloses, in Japanese patent application No. 2007-253528 (Japanese Patent Publication No. 2009-88089A), that a low dielectric constant ceramic layer and a high dielectric constant barium titanate based dielectric material having a low dielectric loss and sinterable at a low temperature can be joined with each other by co-sintering without delamination and cracks.